Article

Role of the bilayer in the shape of the isolated erythrocyte membrane

Department of Biochemistry University of Chicago 60637 Chicago Illinois
Journal of Membrane Biology (Impact Factor: 2.17). 02/1982; 69(2):113-23. DOI: 10.1007/BF01872271
Source: PubMed

ABSTRACT The determinants of cell shape were explored in a study of the crenation (spiculation) of the isolated erythrocyte membrane. Standard ghosts prepared in 5 mM NaPi (pH 8) were plump, dimpled disks even when prepared from echinocytic (spiculated) red cells. These ghosts became crenated in the presence of isotonic saline, millimolar levels of divalent cations, 1 mM 2,4-dinitrophenol or 0.1 mM lysolecithin. Crenation was suppressed in ghosts generated under conditions of minimal osmotic stress, in ghosts from red cells partially depleted of cholesterol, and, paradoxically, in ghosts from red cells crenated by lysolecithin. The susceptibility of ghosts to crenation was lost with time; this process was potentiated by elevated temperature, low ionic strength, and traces of detergents or chlorpromazine. In that ghost shape was influenced by a variety of amphipaths, our results favor the premise that the bilayer and not the subjacent protein reticulum drives ghost crenation. The data also suggest that vigorous osmotic hemolysis induces a redistribution of lipids between the two leaflets of the bilayer which affects membrane contour through a bilayer couple mechanism. Subsequent relaxation of that metastable distribution could account for the observed loss of crenatability.

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    • "It could explain several other observations directly or indirectly related to the erythrocyte shape, suggesting its plausibility [3] [4]. The other view is, however, that bilayer has a dominant role while skeleton plastically accommodates the contours imposed upon it by the overlying membrane [26] [27]. "
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    ABSTRACT: Morphological response (MR) of red blood cells represents a triphasic sequence of spontaneously occurring shape transformation between different shape states upon transfer the cells into isotonic sucrose solution in the order: S(0) (initial discoid shape in physiological saline)-->S(1) (echinocytic shape at the beginning of MR, phase 1)-->S(2) (intermediate discoid shape, phase 2)-->S(3) (final stomatocytic shape, phase 3). In this paper, the dynamics of cell shape changes was investigated by non-invasive light fluctuation method and optical microscopy. Among 12 possible transitions between four main shape states, we experimentally demonstrate here an existence of nine transitions between neighbour or remote states in this sequence. Based on these findings and data from the literature, we may conclude that red blood cells are able to change their shape through direct transitions between four main states except transition S(1)-->S(0), which has not been identified yet. Some shape transitions and their temporal sequence are in accord with predictions of bilayer couple concept, whereas others for example transitions between remote states S(3)-->S(1), S(1)-->S(3) and S(3)-->S(0) are difficult to explain based solely on the difference in relative surface areas of both leaflets of membrane suggesting more complex mechanisms involved. Our data show that MR could represents a phenomenon in which the major role can play pH and chloride-sensitive sensor and switching mechanisms coupled with transmembrane signaling thus involving both cytoskeleton and membrane in coordinated shape response on changes in cell ionic environment.
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    • "The next step toward a full understanding of the cell-shape transformations should be to relate the area difference between the leaflets with the changes in the medium's ionic strength and the transmembrane potential. Lange et al. [34] and Grebe et al. [35] have considered the electrostatic repulsion between charged residues in membrane surface as an expansive force, which can create the area difference between the leaflets. As this electrostatic repulsion can be quantitatively predicted by the electric double layer theory [36], the coupling of the latter with a membrane-mechanical model, like that in [33], would lead to the construction of a complete quantitative theory of the stomatocyte–echinocyte transformation. "
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    • "Consequently, the shape transformation brought about by amphiphilic molecules led to the hypothesis that the lipid bilayer could be the primary determinant of membrane curvature [5]. It is also postulated [6] that the reticulum is able to preserve, but not to impose, the membrane contour. "
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